System and method for vital signal sensing using a millimeter-wave radar sensor

ABSTRACT

A system includes a millimeter-wave radar sensor disposed on a circuit board, a plurality of antennas coupled to the millimeter-wave radar sensor and disposed on the circuit board, and a processing circuit coupled to the millimeter-wave radar sensor and disposed on the circuit board. The processing circuit is configured to determine vital signal information based on output from the millimeter-wave radar sensor.

TECHNICAL FIELD

The present invention relates generally to a system and method for vitalsignal sensing using a millimeter-wave radar sensor.

BACKGROUND

Applications in the millimeter-wave frequency regime have gainedsignificant interest in the past few years due to the rapid advancementin low cost semiconductor technologies such as silicon germanium (SiGe)and fine geometry complementary metal-oxide semiconductor (CMOS)processes. Availability of high-speed bipolar and metal-oxidesemiconductor (MOS) transistors has led to a growing demand forintegrated circuits for millimeter-wave applications at 60 GHz, 77 GHz,and 80 GHz and also beyond 100 GHz. Such applications include, forexample, automotive radar systems and multi-gigabit communicationsystems.

In some radar systems, the distance between the radar and a target isdetermined by transmitting a frequency modulated signal, receiving areflection of the frequency modulated signal, and determining a distancebased on a time delay and/or frequency difference between thetransmission and reception of the frequency modulated signal.Accordingly, some radar systems include a transmit antenna to transmitthe RF signal, a receive antenna to receive the RF, as well as theassociated RF circuitry used to generate the transmitted signal and toreceive the RF signal. In some cases, multiple antennas may be used toimplement directional beams using phased array techniques. A MIMOconfiguration with multiple chipsets can be used to perform coherent andnon-coherent signal processing, as well.

SUMMARY

A system includes a millimeter-wave radar sensor disposed on a circuitboard, a plurality of antennas coupled to the millimeter-wave radarsensor and disposed on the circuit board, and a processing circuitcoupled to the millimeter-wave radar sensor and disposed on the circuitboard. The processing circuit is configured to determine vital signalinformation based on output from the millimeter-wave radar sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1A illustrates an embodiment vital signal measurement system; andFIGS. 1B, 1C and 1D illustrate a smart watch, a chest strap, and a smartphone that incorporate embodiment vital signal measurement systems;

FIG. 2A illustrates a block diagram of an embodiment millimeter-waveradar sensor; FIGS. 2B and 2C illustrate plan views of embodimentmillimeter-wave radar sensor circuits; and FIG. 2D illustrates a blockdiagram of an embodiment vital signal sensing method;

FIGS. 3A, 3B, 3C, 3D and 3E illustrate radar sensor circuit boardsaccording to embodiments of the present invention;

FIGS. 4A and 4B illustrate an embodiment radar sensor implemented usinga waver level package construction;

FIG. 5 illustrates a flowchart of an embodiment method ofmillimeter-wave based vital signal detection;

FIG. 6 illustrates an embodiment heart rate detection processing blockdiagram;

FIGS. 7A and 7B illustrate block diagrams of embodiment confidence leveldetermination algorithms;

FIG. 8 illustrates a block diagram an embodiment self-calibration dataflow method;

FIG. 9 illustrates an embodiment method of calibrating an embodimentadjustable adaptive filter;

FIG. 10A illustrates a block diagram of an embodiment self-calibrationprocedure flow; and FIG. 10B illustrates a corresponding embodimentrun-time procedure flow;

FIG. 11 illustrates a block diagram of an embodiment artery/veindetection method; and

FIG. 12 illustrates a block diagram of a processing system that may beused to implement portions of embodiment vital signal detection systems.

Corresponding numerals and symbols in different figures generally referto corresponding parts unless otherwise indicated. The figures are drawnto clearly illustrate the relevant aspects of the preferred embodimentsand are not necessarily drawn to scale. To more clearly illustratecertain embodiments, a letter indicating variations of the samestructure, material, or process step may follow a figure number.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

The present invention will be described with respect to preferredembodiments in a specific context, a system and method for vital signalsensing using a millimeter-wave radar sensor. The invention may also beapplied to other RF-based systems and applications that detect andidentify the presence of one or more objects based on motion of theobject.

In embodiments of the present invention, a millimeter-wave based radarsensor is used to measure vital signal information such as pulse rate.Such a millimeter-wave based radar sensor may be mounted to asmartphone, a wristwatch, a chest strap or other device. In variousembodiments, the relevant vital signal is determined by using highresponse “range gate” measurements that may be determined, for example,by taking a fast Fourier transform (FFT) of down-converted frequencymodulated continuous wave (FMCW) measurements from the millimeter-wavebased radar sensor. These range gate measurements are then filtereddetermine the relevant vital signal. Such filtering may be adaptivelycalibrated to compensate for irregularities in the physical couplingbetween the millimeter-wave based radar sensor and the body beingmeasured. In some embodiments, the motion of the millimeter-wave basedradar sensor with respect to the body being measured is compensated forby tracking shifts in the high response range gates and stitchingtogether measurements from multiple range gates to form the basis forthe vital signal measurement.

Advantages of embodiment vital signal sensing systems may include theability to perform accurate vital signal measurements in the presence ofrelative motion between the millimeter-wave based radar sensor and thebody being measured. Such advantages are particularly relevant for vitalsensing applications in which heartbeat is measured on a human being inmotion, such as someone who is exercising.

FIG. 1A illustrates a block diagram of radar-based vital signalmeasuring system 100. As shown, radar-based vital signal measuringsystem 100 includes a millimeter-wave radar sensor 102, and a processor104 that controls the operation of millimeter-wave radar sensor 102 andperforms various radar signal processing operations on the data producedby millimeter-wave radar sensor 102. During operation, millimeter-waveradar sensor 102 transmits millimeter-wave RF signals that are reflectedby object 106. While object 106 is depicted as a human hand, it shouldbe understood that object 106 may be any body from which a vital signalis to be measured. The reflected signals are received by millimeter-waveradar sensor 102, converted to a digital representation, and processedby processor 104 to determine, for example, a vital signal produced byobject 106, such as a pulse rate. The result of this processing producesvarious data (represented by signal DATA) indicative of the measuredvital signals.

FIGS. 1B, 1C and 1D illustrate example vital signal sensingconfigurations. For example, FIG. 1B illustrates a rear-view and aside-view of a wristwatch no that includes millimeter-wave radar sensor112. As shown, millimeter-wave radar sensor 112 includes one transmitantenna Tx and two receive antennas Rx1 and Rx2. Alternatively, otherantenna configurations may be used. During operation, millimeter-waveradar sensor 112 transmits millimeter wave radar signals to a user'swrist and determines, for example, a heart rate based on the reflectedRF signal.

FIG. 1C illustrates various views of a chest strap 120 that includesmillimeter-wave radar sensor 122. During operation, millimeter-waveradar sensor 112 transmits millimeter wave radar signals to the chest ofuser 124 and determines a heart rate of user 124 by analyzing radarsignals reflected from the chest of user 124.

FIG. 1D illustrates a rear view of a smart phone 130 on which amillimeter-wave radar sensor 132 is mounted. As shown, millimeter-waveradar sensor 132 includes one transmit antenna Tx and one receiveantenna Rx. Alternatively, other antenna configurations may be used.During operation, millimeter-wave radar sensor 132 transmits millimeterwave radar signals to any portion of the body to which the rear portionof smartphone 130 is facing, and determines for example, a heart ratebased on the reflected RF signal. The results of the vital signalmeasurement may be shown on the screen of 130 via a software applicationor graphical user interface 134.

It should be understood that wristwatch no, chest strap 120 andsmartphone 130 shown in FIGS. 1B, 1C and 1D, respectively, are justthree specific embodiment examples of many possible embodiment systemconfiguration that employ millimeter-wave radar based vital signalsensing.

FIG. 2A illustrates a block diagram of a millimeter-wave radar sensorsystem 200 that may be used to implement millimeter-wave radar sensorcircuits in the various disclosed embodiments. Millimeter-wave radarsensor system 200 includes millimeter-wave radar sensor circuit 202 andprocessing circuitry 204. Embodiment millimeter-wave radar sensorcircuits may be implemented, for example, using a two-dimensionalmillimeter-wave phase-array radar that performs measurements on object106. The millimeter-wave phase-array radar transmits and receivessignals in the 20 GHz to 122 GHz range. Frequencies outside of thisrange may also be used. In some embodiments, millimeter-wave radarsensor circuit 202 operates as a frequency modulated continuous wave(FMCW) radar sensor having multiple transmit and receive channels.Alternatively, other types of radar systems may be used such as pulseradar, continuous wave (CW) radar, frequency modulated continuous wave(FMCW) radar, and non-linear frequency modulated (NLFM) radar toimplement millimeter-wave radar sensor circuit 202.

Millimeter-wave radar sensor circuit 202 transmits and receives radiosignals for determining vital signals of object 106. For example,millimeter-wave radar sensor circuit 202 transmits incident RF signals201 and receives RF signals 203 that are a reflection of the incident RFsignals from object 106. The received reflected RF signals 203 are downconverted by millimeter-wave radar sensor circuit 202 to determine beatfrequency signals. These beat frequency signals may be used to determineinformation such as the location and motion of object 106. In thespecific example of FMCW radar, the beat frequency is proportional tothe distance between millimeter-wave radar sensor circuit 202 and theobject being sensed.

In various embodiments, millimeter-wave radar sensor circuit 202 isconfigured to transmit incident RF signals 201 toward object 106 viatransmit antennas 212 and to receive reflected RF signals 203 fromobject 106 via receive antennas 214. Millimeter-wave radar sensorcircuit 202 includes transmitter front-end circuits 208 coupled totransmit antennas 212 and receiver front-end circuit 210 coupled toreceive antennas 214.

During operation, transmitter front-end circuits 208 may transmit RFsignals toward object 106 simultaneously or individually usingbeamforming depending on the phase of operation. While two transmitterfront-end circuits 208 are depicted in FIG. 2A, it should be appreciatedthat millimeter-wave radar sensor circuit 202 may include less than orgreater than two transmitter front-end circuits 208. Thus, in variousembodiments, the number of transmitters can be extended to n×m. Eachtransmitter front-end circuit 208 includes circuitry configured toproduce the incident RF signals. Such circuitry may include, forexample, RF oscillators, upconverting mixers, RF amplifiers, variablegain amplifiers, filters, transformers, power splitters, and other typesof circuits.

Receiver front-end circuit 210 receives and processes the reflected RFsignals from object 106. As shown in FIG. 2A, receiver front-end circuit210 is configured to be coupled to four receive antennas 214, which maybe configured, for example, as a 2×2 antenna array. In alternativeembodiments, receiver front-end circuit 210 may be configured to becoupled to greater or fewer than four antennas, with the resultingantenna array being of various n×m dimensions depending on the specificembodiment and its specifications. Receiver front-end circuit 210 mayinclude, for example, RF oscillators, upconverting mixers, RFamplifiers, variable gain amplifiers, filters, transformers, powercombiners and other types of circuits.

Radar circuitry 206 provides signals to be transmitted to transmitterfront-end circuits 208, receives signals from receiver front-end circuit210, and may be configured to control the operation of millimeter-waveradar sensor circuit 202. In some embodiments, radar circuitry 206includes, but is not limited to, frequency synthesis circuitry,up-conversion and down-conversion circuitry, variable gain amplifiers,analog-to-digital converters, digital-to-analog converters, digitalsignal processing circuitry for baseband signals, bias generationcircuits, and voltage regulators.

Radar circuitry 206 may receive a baseband radar signal from processingcircuitry 204 and control a frequency of an RF oscillator based on thereceived baseband signal. In some embodiments, this received basebandsignal may represent a FMCW frequency chirp to be transmitted. Radarcircuitry 206 may adjust the frequency of the RF oscillator by applyinga signal proportional to the received baseband signal to a frequencycontrol input of a phase locked loop. Alternatively, the baseband signalreceived from processing circuitry 204 may be upconverted using one ormore mixers. Radar circuitry 206 may transmit and digitize basebandsignals via a digital bus (e.g., a USB bus), transmit and receive analogsignals via an analog signal path, and/or transmit and/or receive acombination of analog and digital signals to and from processingcircuitry 204.

Processing circuitry 204 acquires baseband signals provided by radarcircuitry 206 and formats the acquired baseband signals for transmissionto an embodiment signal processing unit. These acquired baseband signalsmay represent beat frequencies, for example. In some embodiments,processing circuitry 204 includes a bus interface (not shown) fortransferring data to other components within the occupancy detectionsystem. Optionally, processing circuitry 204 may also perform signalprocessing steps used by embodiment occupancy detection systems such asa fast Fourier transform (FFT), a short-time Fourier transform (STFT),macro-Doppler analysis, micro-Doppler analysis, vital sign analysis,object classification, machine learning, and the like. In addition toprocessing the acquired baseband signals, processing circuitry 204 mayalso control aspects of millimeter-wave radar sensor circuit 202, suchas controlling the transmissions produced by millimeter-wave radarsensor circuit 202.

The various components of millimeter-wave radar sensor system 200 may bepartitioned in various ways. For example, millimeter-wave radar sensorcircuit 202 may be implemented on one or more RF integrated circuits(RFICs), antennas 212 and 214 may be disposed on a circuit board, andprocessing circuitry 204 may be implemented using a processor, amicroprocessor, a digital signal processor and/or a custom logic circuitdisposed on one or more integrated circuits/semiconductor substrates.Processing circuitry 204 may include a processor that executesinstructions in an executable program stored in a non-transitorycomputer readable storage medium, such as a memory to perform thefunctions of processing circuitry 204. In some embodiments, however, allor part of the functionality of processing circuitry 204 may beincorporated on the same integrated circuit/semiconductor substrate onwhich millimeter-wave radar sensor circuit 202 is disposed.

In some embodiments, some or all portions of millimeter-wave radarsensor circuit 202 may be implemented in a package that containstransmit antennas 212, receive antennas 214, transmitter front-endcircuits 208, receiver front-end circuit 210, and/or radar circuitry206. In some embodiments, millimeter-wave radar sensor circuit 202 maybe implemented as one or more integrated circuits disposed on a circuitboard, and transmit antennas 212 and receive antennas 214 may beimplemented on the circuit board adjacent to the integrated circuits. Insome embodiments, transmitter front-end circuits 208, receiver front-endcircuit 210, and radar circuitry 206 are formed on a same radarfront-end integrated circuit (IC) die. Transmit antennas 212 and receiveantennas 214 may be part of the radar front-end IC die, or may beimplemented as separate antennas disposed over or adjacent to the radarfront-end IC die. The radar front-end IC die may further includeconductive layers, such as redistribution layers (RDLs), used forrouting and/or for the implementation of various passive or activedevices of millimeter-wave radar sensor circuit 202. In an embodiment,transmit antennas 212 and receive antennas 214 may be implemented usingthe RDLs of the radar front-end IC die.

FIG. 2B illustrates a plan view of millimeter-wave radar sensor circuit220 that may be used to implement millimeter-wave radar sensor circuit202. As shown, millimeter-wave radar sensor circuit 220 is implementedas an RFIC 224 coupled to transmit antennas 212 and receive antenna 214implemented as patch antennas disposed on or within substrate 222. Insome embodiments, substrate 222 may be implemented using a circuit boardon which millimeter-wave radar sensor circuit 202 is disposed and onwhich transmit antennas 212 and receive antennas 214 are implementedusing conductive layers of the circuit board. Alternatively, substrate222 represents a wafer substrate on which one or more RDLs are disposedand on which transmit antennas 212 and receive antennas 214 areimplemented using conductive layers on the one or more RDLs.

FIG. 2C illustrates a plan view of millimeter-wave radar sensor circuit232 that includes an array of transmit antennas 212 and an array ofreceive antennas 214 coupled to RFIC 234 disposed on substrate 236. Invarious embodiments, transmit antennas 212 may form an array of mantennas and receive antennas 214 may form an array of n antennas. Eachof the m transmit antennas 212 is coupled to a corresponding pin on RFIC234 and coupled to a corresponding transmit circuit within RFIC 234; andeach of the n receive antennas 214 is coupled to a corresponding pin onRFIC 234 and coupled to a corresponding receive circuit within RFIC 234.In various embodiments, the array of transmit antennas 212 and the arrayof receive antennas 214 may be implemented as a uniform array or alinear array of any dimension. It should be appreciated that theimplementations of FIGS. 2B and 2C are just two examples of the manyways that embodiment millimeter-wave radar sensor circuits could beimplemented.

FIG. 2D illustrates a method 250 of performing vital signal measurementthat may be used in conjunction with an embodiment millimeter-wave radarsensor circuit such as millimeter-wave radar sensor circuit 202, 220, or232 described above with respect to FIGS. 2A, 2B and 2C. In step 252,the millimeter-wave sensor circuit performs a set of radar measurements,such as FMCW radar measurements. In step 254 an FFT is taken of thebaseband representation of these measurements, which are in the form ofbeat frequencies. Such an FFT may be referred to as a “range FFT”because each bin of the resulting FFT represents energy reflected by anobject at a particular range or distance. In alternative embodiments,other transforms may be used besides an FFT, such as a discrete cosinetransform (DCT), Short Time Fractional Fourier Transform (STFrFT),z-transform or other transform types known in the art. In step 256, thehighest amplitude FFT bins or “range gates” are determined. These highresponse range gates represent the distance to the largest objects inthe range of the millimeter-wave radar sensor. Thus, in variousembodiments in which the monitored object is a portion of the human bodythat includes arteries or portions of the body that move during due toblood flow, the motion of these high response range gates may containinformation related to the monitored object's heart rate. In someembodiments, determining the high response range gates includesdetermining which range gates of a first set of range gate measurementshave a higher peak-to-average ratio or a higher amplitude compared tothe mean amplitude. For example, in some embodiments, thepeak-to-average ratio is greater than 1.3 and/or the amplitude is twicethe mean amplitude. Alternatively, difference peak-to-average ratios andamplitudes may be used.

In step 258 a correction filter is applied to the high response rangegates. This correction filter may provide equalization and/or compensatefor losses or distortion in the physical coupling between themillimeter-wave radar sensor and the target. In some embodiments, thiscorrection filter is an adaptive filter, such as an adaptive FiniteImpulse Response (FIR) filter, that is calibrated according to aparticular use case. For example, the correction filter may becalibrated to correct for the coupling between a millimeter-wave radarsensor mounted in a smart-watch or wrist band and the user's wrist.Another correction filter may be calibrated to correct for the couplingbetween the millimeter-wave radar sensor mounted in a chest strap or andthe user's chest. The correction filter may be calibrated to correct forthe coupling between the millimeter-wave radar sensor and other mountingor use scenarios. In some embodiments this correction filter may becalibrated using an adaptation algorithm during the manufacture of thevital signal sensing device and/or during a user calibration of thevital signal sensing device, as will be described below. In someembodiments, the particular use case (e.g., wrist strap, chest strap,etc.) may be automatically detected base on the set of radarmeasurements performed in step 252 and the applicable correction filter(or correction filter coefficients) are selected based on the particularuse case. In step 260, the output of the correction filter is furtherfiltered by a vital signal filter to extract vital signal informationsuch as heart beat signals.

FIGS. 3A to 3E illustrate side views of various embodiment substrateconfigurations that may be used to implement radar sensors forembodiment millimeter-wave radar based vital signal sensing systems,such as radar sensors 110, 112, 122 and 132 shown in FIGS. 1A, 1B, 1Cand 1D, respectively. In accordance with one embodiment, FIG. 3Aillustrates a side view of a radar sensor circuit board 300 thatincludes three conductive layers, M1, M2 and M3 and two laminate layers302 and 304. As shown, conductive layer M1 is used as an antenna layerand is used to implement transmit antenna TX1 and receive antennas RX1and RX2. Conductive layer M2 is used, for example, as a ground plane,and conductive layer M3 is used to make contact with solder balls 312.In the illustrated embodiment, RF and baseband integrated circuit 308,digital signal processor (DSP) integrated circuit 306 and memoryintegrated circuit 310 are embedded within laminate layer 304.Integrated circuits 308 and 310 may be embedded in a laminate using anembedding process known in the art. For example, the embedding processmay include making a cavity in the laminate and placing the integratedcircuit therein. The process may also include growing a substrate afterthe integrated circuits are embedded. Contact between RF and basebandintegrated circuit 308 and antennas Tx1, Rx1 and Rx2 is made using vias314. In alternative embodiments, laminate layers 302 and 304 may beimplemented differently. For example, layers 302 and 304 may beimplemented using low temperature co-fired ceramic (LTCC) substrates.

In various embodiments, RF and baseband integrated circuit 308 includesthe RF and analog components of a millimeter-wave radar sensor includingthe RF/radar front end, the various frequency generation circuitry, as aone or more oscillators and phase locked loops (PLLS), upconversion anddownconversion circuitry, baseband circuitry and various supportcircuitry. RF and baseband integrated circuit 308 may also includeanalog-to-digital converters that convert analog signals derived fromthe received radar signal to the digital domain in the form of raw data.

DSP integrated circuit 306 is coupled to RF and baseband integratedcircuit 308 and is configured to receive the raw data produced by RF andbaseband integrated circuit 308. In various embodiments, DSP integratedcircuit 306 is configured to perform embodiment vital signal analysisand machine learning functions described below. DSP integrated circuit306 may also be configured to perform calibration, adaptive filteringand signal processing algorithms that support the operation of theembodiment radar system. DSP integrated circuit 306 may be implementedusing digital signal processing circuitry and/or other processingcircuitry known in the art. DSP integrated circuit 306 also enables theexecution of various computationally intensive algorithms within theradar system, which reduces the computational loading of and the amountof data exchanged with external application processors.

Memory integrated circuit 310 may include volatile and/or non-volatilememory on which configuration data and intermediate calculations dataare stored. In some embodiments, memory integrated circuit 310 may beconfigured to store several days, months or years worth of vital signaldata in order to support the various machine learning algorithmsimplemented by DSP integrated circuit 306. In addition, statistics maybe generated using the data stored in memory circuit 310. Memoryintegrated circuit 310 may also help support the storage of data for anexternal application processor in addition to supporting operation ofDSP integrated circuit 306.

In some embodiments, the conductive layers M1, M2 and M3 may be formedfrom a metal foil, metal layer, or metallization that has been laminatedto a laminate layer. In one embodiment, the conductive layers comprisecopper (Cu). In some embodiments, the conductive layers comprise otherconductive materials such as silver (Ag) and aluminum (Al). In someembodiments, the conductive layers may comprise different conductivematerials.

The laminate layers may separate the conductive layers and providestructural support for radar sensor circuit board 300. In variousembodiments, the laminate layers are implemented using an insulatormaterial. For example, a low-loss high frequency material such as awoven glass reinforced hydrocarbon ceramic and/orpolytetrafluoroethylene (PTFE) may be used. In some embodiments, thelaminate layers comprise a pre-impregnated composite material (PPG). Oneor more of the laminate layers may be commercial laminate materialmanufactured with copper cladding on one or both surfaces. In someembodiments, all laminate material layers may comprise the sameinsulator material, while in other embodiments, different laminatematerial layers may be implemented using different insulating materials.

One type of laminate material that may be used to form the conductivelayers and laminate layers in radar sensor circuit board 300 is copperclad laminate. Sheets of copper clad laminate material may be fabricatedas single-sided or double-sided copper clad sheets. During thefabrication process, copper sheets may be placed on one or both sides ofthe laminate material. Some combination of heat and pressure may then beapplied to facilitate attachment of the copper sheets to the laminatematerial.

A conductive layer on a surface of a laminate layer may be anelectrodeposited (ED) foil or a rolled foil, for example. A rolled foilsheet may be produced by repeatedly feeding the foil sheet throughrollers to evenly reduce the thickness of the foil sheet. ED foil may bemore rigid and have a different grain structure. In contrast, rolledfoil may be smooth and flexible. In some cases, rolled foil may beadvantageous in RF applications, due to decreased surface roughness.

One or more vias 314 connect the first conductive layer M1 and thesecond conductive layer M2 and/or the RF and baseband integratedcircuit. For example, prior to attaching laminate layer 302 to laminatelayer 304, one or more vias 314 may be formed as through substrate vias(TSVs) passing through laminate layer 302 from the second conductivelayer M2 on the back side surface of laminate layer 302 to an opposingsurface of laminate layer 302. Vias 314 may be exposed at the opposingsurface such that electrical contact is made with third conductive layerM3 upon attachment laminate layer 302 to laminate layer 304.

FIG. 3B illustrates a side view of a radar sensor circuit board 320 thatincludes three conductive layers, M1, M2, M3 and M4 and two laminatelayers 302 and 304. Conductive layer M1 is used as an antenna layer toimplement transmit antenna TX1 and receive antenna RX1. Conductive layerM2 is used, for example, as a ground plane and/or an interconnect layer,and conductive layer M3 is used as an interconnect layer. Conductivelayer M4 is used to make contact with solder balls 312. In theillustrated embodiment, RF and baseband integrated circuit 308, digitalsignal processor integrated circuit 306 and memory integrated circuit310 are mounted on the bottom surface of laminate layer 304. Contactbetween RF and baseband integrated circuit 308 and antennas Tx1 and Rx1is made using vias 322. Integrated circuits 306 and 308 and 310 may beattached to laminate layer 304 using chip-on-board methods known in theart.

FIG. 3C illustrates a side view of a radar sensor circuit board 330 thatutilizes a four layer laminate structure having four conductive layersM1, M2, M3 and M4 and three laminate layers 302, 304 and 332. Additionallaminate layer 332 may be constructed in a similar manner using similarmaterials as laminate layers 302 and 304 described above. In theembodiment of FIG. 3C, conductive layers M1, M2 and laminate layer 302and 304 are used to implement an antenna stack. In an embodiment antennastack, conductive layer M4 functions as a ground plane, conductive layerM3 functions as a feeding line, conductive layer M2 functions as aground plane, and conductive layer M1 functions as a patch antenna.Conductive layer M3 may include a slot to couple the energy of thefeeding line to the patch antenna of conductive layer M1. Laminate layer302 define the bandwidth of antenna and laminate layers 304 and 332 maybe selected to match the feeding line in M3. In some implementations,laminate layers 304 and 332 are selected to provide an optimum match. Asshown, RF and baseband integrated circuit 308, digital signal processorintegrated circuit 306 and memory integrated circuit 310 are mounted onthe bottom surface of laminate layer 332. Contact between RF andbaseband integrated circuit 308 and the feeding line of the antenna ismade using vias 322.

FIG. 3D illustrates a side view of a radar sensor circuit board 34o thatutilizes three conductive layers M1, M2 and M3 and two laminate layers302 and 304 and die to die stacking. As shown, RF and Basebandintegrated circuit 308 is stacked on top of DSP integrated circuit 306and memory integrated circuit 310 within laminate layer 304. Contactbetween RF and baseband integrated circuit 308 and transmit antenna Tx1and receive antenna Rx1 is made using vias 322.

FIG. 3E illustrates a side view of a radar sensor circuit board 35o thatutilizes three conductive layers M1, M2 and M3 and two laminate layers302 and 304 and multilayer chip stacking. As shown, RF and Basebandintegrated circuit 308 is mounted on the bottom surface of laminatelayer 304. Memory integrated circuit 310 and DSP integrated circuit 306are disposed within the top surface of laminate layer 304. Contactbetween RF and baseband integrated circuit 308 and transmit antenna Tx1and receive antenna Rx1 is made using vias 322.

FIG. 4A illustrates a cross-sectional view of an embodiment RFsystem/antenna package 400. In a specific embodiment directed toward anembedded wafer level ball grid array (eWLB) package, RF system/antennapackage 420 includes a molding material layer 402 that is and aredistribution layer (RDL) 406 disposed beneath molding material. Insome embodiments, molding material layer 402 is composed of mold andlaminate materials and is between about 200 μm and 600 μm thick, and RDL406 is composed of an conducting material, such as copper and is betweenabout 5 μm and about 15 μm thick. As shown, integrated circuit die 306,308 and 310 are disposed in a single layer within a cavity withinmolding material 402. Receive patch antenna Rx, transmit patch antennaTx are located in the fan out area of the eWLB package, and connectionsbetween integrated circuit die 306, 308 and 310 are made in a firstlayer of metal M1 at a first surface of (RDL) 406. In embodiments, RFsystem/antenna package 400 may include further conductive layers usedfor routing and/or for the implementation of various passive deviceswithin the substrate of the package. For example a second level of metalM2 on the opposite side of RDL 404 from first level of metal M1 is usedto made contact to solder balls 312. It should be understood that thespecific dimensions detailed herein are just examples. In alternativeembodiments of the present invention, other dimensions could be used. Infurther alternative embodiments of the present invention, other packagetypes such as a BGA or Advanced Thin Small Leadless ATSPL package mayalso be used.

FIG. 4B illustrates a plan view of embodiment radar sensor 400. Asshown, antennas Rx and Tx as implemented as patch antennas in metallayer M1. It should be understood that the embodiment shown in FIG. 4Bis just one example of the many possible ways the various components canbe arranged. In alternative embodiments RF and Baseband integratedcircuit 308, memory integrated circuit 310, DSP integrated circuit 306,transmit antenna Tx and receive antenna Rx may be arranged differently.

It should be appreciated that the radar sensor circuit board examplesshown in FIGS. 3A to 3E and FIGS. 4A and 4B are just a few of the manypossible configurations for implementing embodiment radar sensor circuitboards. For example, while FIG. 3B-3E and FIGS. 4A and 4B each show asingle transmit antenna and a signal receive antenna, in alternativeembodiments, different numbers of receive and transmit antennas may beimplemented depending on the particular requirements of the radarsystem. In some embodiments, the number and transmit and/or receivechannels and antennas may be increased in order to implement beamsteering. By using beam steering, the radar beam may be directed in aparticular direction. This may be used, for example, to direct the radarbeam toward fine veins and arteries in order to perform more accurateand precise vital signal measurements.

FIG. 5 illustrates a flowchart of an embodiment method 500 ofmillimeter-wave based vital signal detection. In step 502, baseband FMCWradar data is collected over a sampling window. In some embodiments,this window is between about 3 seconds and 5 seconds in length, however,other window lengths may be used. The downconverted FMCW radar data maybe in the form of digitized time samples that form a periodic signalhaving an instantaneous frequency proportional to a distance between themillimeter wave radar sensor and a detected object. In step 504, rangegates with high responses are extracted from the windowed FMCW data. Invarious embodiments, this may be accomplished by taking an FFT or othertransform of the FMCW data and determining which frequency bins have ahighest response. Since each frequency represents a “range gate” ordetermined distance, the highest response range gate responses representthe distance of the user whose vital signals are to be measured. In thecase of most wearable devices in which only one target is to be tracked,there will likely be either a single high response range gate or acluster of high response range gates that represent the distance fromthe millimeter-wave radar sensor to the nearest target. These highresponse range gates may shift over time due to the relative motionbetween the millimeter-wave radar sensor and the user. Thus, in someembodiments, the identity of the high response range gates are trackedover time as described in further detail below.

Once the high response range gates are extracted in step 504, the motionrepresented by these high response range gates may be analyzed todetermine vital signals such as heart rate. For example, in step 512,the high response range gate signals are bandpass filtered to extract aheartbeat signal. In some embodiments, the bandwidth of the heartbandpass filter may be between about 0.8 Hz and about 3.33 Hz.Bandwidths outside of these ranges may also be used depending on theparticular embodiment and its specifications. In step 514, identifiedrange gates in which no signals are detected are identified as staticnon-human objects and in step 516, a heart rate is derived from thefiltering operation of step 512. In some embodiments, a confidence levelof the heart rate may also be derived as explained below.

FIG. 6 illustrates a heart rate detection processing block diagram 600according to an embodiment. As shown, block 602 determines maximum valuerange gates and provides the identity of these maximum value range gatesin slow-time. In some embodiments, a range FFT is taken over each FMCWchirp, and the maximum valued range gates are determined for each chirp.As time progresses, the maximum value range gates may shift according tothe detected heart beat as the relative distance between themillimeter-wave radar sensor and the user moves back and forth due tomotion caused by the user's beating heart. Heartbeat signal filter 604,which may be a bandpass filter that performs the filtering steps of step512 in FIG. 5, provides an extracted heartbeat signal. Smoothing filter606 further filters the heartbeat signal and heartbeat rate estimationblock 608 determines a heartrate from the smoothed heartbeat signal. Insome embodiments, smoothing filter 606 is implemented by aSavitzky-Golay filter that essentially performs a k-point regression.Alternatively, other smoothing filters may be used. In some embodiments,block 608 determines the heartrate by measuring the time period of aheartbeat. Alternatively, other methods of determining a frequency of aperiodic signal may be used.

Confidence indicator block 610 determines a confidence level of theestimated heart beat using methods described below. In one embodiment,confidence level indicator block 610 provides a confidence level of anestimated heart rate by determining a duration of an amplitude band foran extracted range gate, and determining the percentage of time that thetime-window length is within the amplitude band. For example,determining the confidence level may include determining a percentage oftime in which the peak-to-average ratio of the determined high responserange gates is within a predetermined range. In one example, theamplitude band is taken to be between about 0.8 and 1.2 of a normalizedaverage for a particular range gate or for a group of range gates. Ifthe normalized amplitude of the range gate or the group of range gatesis within the amplitude band of 0.8 to 1.2 for 95% of the time window,then a 90% confidence level is assigned to the heartbeat measurement. Ifthe normalized amplitude is within the amplitude band for 75% of thetime window, then a 70% confidence level is assigned, and if thenormalized amplitude is within the amplitude band for 55% of the timewindow, then a 50% confidence level is assigned. It should be understoodthat the numerical values of the normalized amplitude band and thevarious confidence levels are just one of many possible normalizedamplitude band and confidence level definitions that may be used. Inalternative embodiments, other values may be assigned. In variousembodiments, all of the blocks shown in FIG. 6 may be implemented, forexample, using DSP or other processor.

FIGS. 7A and 7B illustrate two example confidence level determinationalgorithm methods. FIG. 7A illustrates a first embodiment method 700. Asshown, in step 704, the maximum range gate values are determined for aset of FMCW data 702 in a short time window. This short time window,which is narrower than the 3-5 second time window described above, maybe about 500 μs long in one example. Alternatively, other window timelengths may be used. In step 706, the consistency for each range gate isdetermined, for example, by determining the percentage of time theamplitude of the particular range gate is within a normalized amplitudeband as described above. In step 710, a determination is made as towhether the range gate values are consistent. This determination can bemade, for example, by comparing the percentage of time that theamplitude of a particular range gate is within the normalized amplitudeto a predetermined threshold. For example, the percentage may becompared with a predetermined threshold of 95%. Alternatively, otherpercentage threshold may be used.

If step 710 determines that the particular range gate values areconsistent, additional data from the 3-5 second time window is appendedto the short time window data in step 708 and the next group of shorttime window data 702 is analyzed. Thus, in various embodiments, a fewseconds of data from short time windows may be stitched together to formlonger lengths of vital signal data for analysis. In some embodiments,data from the neighboring range gates along with the high response rangegates may be stitched together to form a set of modified range gatedata. By stitching together data in this fashion, long term motion, asexemplified by shifts in the maximum value range gates, can becompensated for. Thus, in some embodiments, range gate informationrelevant to vital signal measurements may be segregated from irrelevantrange gate information, and the irrelevant range gate informationdiscarded.

If step 710 determines that the particular range gate values areconsistent, additional data from the 3-5 second time window is appendedto the short time window data in step 708 if phase continuity can bepreserved between groups of data as determined in step 714. In variousembodiments phase continuity may be preserved, for example, by adding orsubtracting a number of samples from the beginning of a second waveformsegment and by subtracting or adding a corresponding number of samplesfrom the end of a first waveform segment until phase continuity isachieved. In some embodiments, zeros may be appended to the end thefirst waveform segment and/or appended to the beginning of the secondwaveform segment. By preserving phase continuity in this manner,spectral regrowth due to phase discontinuities can be reduced, therebyallowing for more accurate vital signal measurements.

In some embodiments, phase continuity is determined as follows:

${\hat{P} = {\frac{1}{N_{w} - 1}{\sum\limits_{j = 1}^{N_{w} - 1}{d\left( {\theta_{j},\theta_{j + 1}} \right)}}}},$

where {circumflex over (P)} is the average pairwise phase distance,θ_(j) and θ_(k) are the relative phases, and d(θ_(j), θ_(k)) representsthe Euclidean distance (squared distance) or the Manhattan distance(absolute distance). In some embodiments, phase continuity is deemed toexist when {circumflex over (P)} is less than a predetermined phasecontinuity threshold. In some embodiments, this predetermined phasecontinuity threshold may be between about 0.01 rad/sec and about 0.5rad/sec. Alternatively, other thresholds outside of this range may beused depending on the particular embodiment and its specifications. Oncedata is stitched together from multiple short time windows in step 708,the resulting stitched together data is filtered in step 716 to extractvital signals according to the embodiments described herein.

FIG. 7B illustrates a confidence level determination algorithm method730 according to a further embodiment in which a confidence levelmeasurement for an entire 3-4 second data window is determined. However,in method 730, the same set of range gates may be used over the courseof the entire 3-4 seconds of windowed data 732.

As shown, in step 734, the maximum range gate values are determined fora set of FMCW data 732 in a long time window, for example a 3-4 secondtime window. Alternatively, other time window lengths can be used. Instep 736, the consistency for each range gate is determined, forexample, by determining the percentage of time the amplitude of theparticular range gate is within a normalized amplitude band as describedabove. In step 716, range gate data is filtered to extract vital signalsaccording to embodiments described herein, and in step 738, a confidencelevel/value is generated the corresponds to particular long window data732 being evaluated using confidence level indication techniquesdescribed above.

In various embodiments, method 730 shown in FIG. 7B consumes less powerwhen implemented than method 700 shown in FIG. 7A. In some embodiments,both method 700 shown in FIG. 7A and method 730 shown in FIG. 7B may beperformed within the same system. For example, method 730 shown in FIG.7B may be performed under low power and low power conditions or insituations where there is very little movement between themillimeter-wave radar sensor and the target being measured. In someembodiments, low power conditions may include low battery conditions. Insituations where there is very little movement, it is less necessary tostitch together data from different range gates over the course of along 3-4 second window of data because the same range gates providevital signal data over longer periods of time. In an alternativeembodiment, data from the same range bins may be stitched together overmultiple data windows.

In some embodiments, the confidence level produced during step 738 maybe used to determine whether to keep using method 730 of FIG. 7B orwhether to transition to method 700 of FIG. 7A. For example, if theconfidence level is less than a predetermined threshold and/or of theconfidence level is less than the predetermined threshold for more thana predetermined number of samples (e.g., over long time window data,short time window data, or a subset thereof), the system may transitionto method 700 shown in FIG. 7A in order to increase the detectionperformance of the system by stitching together data from differentrange gates.

FIG. 8 illustrates an embodiment self-calibration data flow method 800that may be used to optimize vital Doppler filters for a particularphysical vital sensor implementation such as a wrist strap, arm strap,chest strap, etc. In step 802, data is captured from the millimeter-wavedata sensor. Capturing data may include, for example, receiving digitaldata from a data bus coupled to the millimeter-wave data sensor. In step804, interference mitigation is performed. This includes pre-whiteningthe received radar sensor data for mitigating antenna correlation andcolored clutter response. In step 806 range windowing and zero paddingis performed in preparation of the range FFT for the sensor datareceived from each sensor. In this step, a window function is applied tothe received radar data followed by zero-padding to improve accuracyalong range axis. In step 808, a range FFT is performed on the datareceived by each sensor and/or each antenna of each sensor on thewindowed and zero-padded range data. In step 810, the maximum rangegates are determined by evaluating the amplitude of each FFT binproduced by the range FFT of step 808 and determining the maximum FFTbin(s) for each chirp.

In step 812, a frequency response of the determined maximum determinedrange gates is correlated with reference signals 814. In variousembodiments, reference signals 814 are stored reference signals thatcorrespond to a particular use or coupling configuration case such as awrist-strap, arm strap and/or other coupling scenarios between the radarsensor and the target. In some embodiments, these stored referencesignals may include stored reference vital signals such as a referenceheartbeat signal. In some embodiments, the reference heartbeat signal isa standard FDA approved heartbeat signal of 60 beats/min.

In an embodiment, slow time data from the selected range bins arecorrelated with reference signals corresponding to the expected responseemanating from an arm, chest or wrist. The response having the highestcorrelation is selected and the corresponding vital Doppler Filters andthe corresponding vital Doppler Filter transform are updated. Differentfilters and transforms are used due to the different coupling and EMscattering characteristic between the radar sensor and the particularpart of the body being monitored. For example, the coupling between theradar sensor and a user's arm is different from the coupling between theradar sensor and a user's chest.

In step 816, filtering functions for the Doppler filters and Dopplertransforms are determined based on the correlated frequency responsecalculated in step 812. Embodiment Doppler filters and Dopplertransforms may be implemented using non-linear functions. In someembodiments, method 800 is performed during a factory calibration flow.In various embodiments, the filter setting for the vital Doppler filtersand the vital Doppler filter transforms may be used to compensate forsignal loss due to the manner in which the physical radar sensor iscoupled to the target.

FIG. 9 illustrates an embodiment method 900 of calibrating an embodimentadjustable adaptive filter. In an embodiment, an adaptive algorithm 910is used to adjust a heartbeat signal adaptive filter 904 such that theerror between the output of the heartbeat signal adaptive filter 904 anda reference heart signal/value 908 is minimized or reduced. In otherwords, the heartbeat signal adaptive filter is calibrated to have asimilar signal behavior as reference heart signal value 908 for aparticular use case (e.g., wrist strap, arm strap, chest strap, etc.).For example, heartbeat signal adaptive filter may be tuned to produce ameasurable heartbeat signal given range gate slow-time data 902 that wasgenerated for the particular use case. Heartbeat signal adaptive filter904 may also be referred to as correction filter that is configured tocorrect the range gate data for the manner in which the millimeter-waveradar sensor is coupled to the biological target. Range-gate slow-timedata 902 represents captured FMCW data from the system being calibratedfor a particular use case. In some embodiments, heartbeat signaladaptive filter 904 is used to compensate for the non-lineartransformation undergone by the received radar data due to backscattering. Moreover, in some embodiments, an embodiment calibrationprocedure may be performed on a human subject.

In some embodiments, reference heart signal/value 908 represents atemplate heartbeat signal that is based on a normal heartbeat. Thistemplate heartbeat signal may be generated by an approved medicalorganization based on clinically approved measurements. Reference heartsignal/value 908 may represent, for example, a normal heartbeat of about72 beats per minute. Alternatively, other heart rates may be used. Insome embodiments, method 900 may be performed during a factorycalibration of an embodiment millimeter-wave radar based vital signalsensing system and/or may be performed periodically during used when orif the performance of the millimeter-wave radar based vital signalsensing system degrades over time, or the conditions for comparableresults are not obtainable.

In some embodiments, adaptive algorithm 910 may include, for example, aleast mean square algorithm, a filter stochastic gradient algorithm, adescent algorithm, or other adaptive algorithm known in the art. Forexample, a least squares based cost function used by an embodiment leastmean square algorithm may be expressed as:

J _(LMS)(n)=Σ_(i=1) ^(N)α(i)(d(i)−y(i))²,

where d(i), y(i) are the reference heart-beat signal and referencesignal respectively, α(i) is the pre-defined coefficients that definethe LMS cost function. In some embodiments, the heartbeat signaladaptive filter 904 in conjunction with adaptive algorithm may operateaccording to the following adaptive filter update rule:

w _(i)(n+1)=w _(i)(n)+μ(n)g ₁(J _(LMS)(n))g ₂(y(n−i)),

where w_(i)(n) refers to the i^(th) coefficient of the adaptive filterat n^(th) iteration of LMS. The above equation is the filter weightupdate equation, μ(n) is the step-size which can be independent of theiteration as well, g₁(.) and g₂(.) are some functions based on LMS type.For instance bate-LMS, g₁(.) is a derivative w.r.t. y(i), and g₂(.) isthe identity function. For sign-RMS, g₂(.) is the sign function, etc.

In some embodiments, an optional transform function 906 may be used toreduce adaptive filter convergence or reduce computational complexity.The transform function may be expressed as:

y(n)=ƒ(W(n),y(n−1), . . . y(1)),

where ƒ(.) defines the transformation which is a function of the inputdata {y(n−1), . . . y(1)} and the kernel W(n). In various embodiment,transform function 906 may be used to maximize FFT operation when thefilter is being fit to an absolute heart-beat while disregarding thesubtleties of other frequency components in the heart signal. In someembodiments, a DCT transformation could be used to represent theheartbeat signal using a lower number of coefficients, thereby reducingthe computational complexity of the filter and reducing its convergencetime.

FIG. 10A illustrates a self-calibration procedure flow 1000 and FIG. 10Billustrates a corresponding run-time procedure flow 1030 according to anembodiment of the present invention. The procedure flows of FIGS. 10Aand 10B may be used in any embodiment millimeter-wave based vital signalsensing system.

During self-calibration procedure flow 1010 shown in FIG. 10A, a rangeFFT 1012 is performed on radar analog-to-digital converter (ADC) data1010 that was captured using an embodiment millimeter-wave radar sensor,such as those described above. Artery/vein detection algorithm, which isdescribed with respect to FIG. 11 below, determines a heartbeat signal,which is filtered by heartbeat signal filter 1014. Heartbeat signalfilter 1014 may be implemented, for example, using a bandpass filter toextract a filtered heartbeat signal. Smoothing filter 1016 smooths theoutput of the heartbeat signal filter 1014 and heartbeat estimationblock 1016 determines a heartrate from the smoothed heartbeat signal.Smoothing filter 1016 may be implemented, for example using a 15^(th)order Savitzky-Golay filter, which essentially implements a 15 pointregression. Alternatively, other filter types can be used.

In some embodiments, heartbeat estimation block 1016 determines theheartrate by measuring the time period of a heartbeat. Alternatively,other methods of determining a frequency of a periodic signal may beused. Confidence level indicator 1020 determines a confidence level ofthe estimated heart beat using confidence level determination methodsdescribed above. In some embodiments, the determined confidence levelmay be used to select the algorithm used by heartbeat rate estimationblock 1018. For example, when confidence level indicator 1020 indicatesa high confidence a high confidence level, a lower complexity algorithmcould be used by heartbeat rate estimation block 1018 in order to savepower.

During self-calibration procedure 1002, error determination block 1008produces an error signal by determining a difference between referencesignal 1004 and the estimated heartrate determined by heartbeatestimation block 1016. In some embodiments, error determination block1008 may be implemented by subtracting reference signal 1004 from theoutput of heartbeat rate estimation block 1018. In various embodiments,adaptive algorithm 1006 updates the filter coefficients of heartbeatsignal filter 1014 in order to reduce the error signal determined byerror determination block 1008. The operation of adaptive algorithm 1006in conjunction with reference signal 1004 and heartbeat signal filter1014 may proceed in a similar manner as the calibration method describedabove with respect to FIG. 9. In some embodiments, a plurality of setsof coefficients directed toward various use cases may be derived usingself-calibration procedure 1002. For example, a first set of filtercoefficients for heartbeat signal 1014 may be derived for a wrist strap,a second set of filter coefficients may derived for an arm strap, athird set of filter coefficients may be derived for a chest strap and soon.

During self-calibration, the user may attach the millimeter-wave radarsensor to his or her body in the applicable manner (e.g., wrist strap,arm strap, chest strap, etc.) and initiate the self-calibrationprocedure. Thus, each set of radar ADC data 1010 taken during theself-calibration procedure represents FMCW data derived for a particularuse case. Once one or more self-calibration procedures are complete, thevarious sets of filter coefficients for heartbeat signal filter 1014 maybe stored in memory for later retrieval during operation.

FIG. 10B illustrates the corresponding run-time procedure flow 1030 thatrepresents the procedure flow that an embodiment vital signal detectionsystem may use during normal operation. Range FFT 1012, artery/veindetection 1014, heartbeat signal filter 1014, smoothing filter 1016,heartbeat rate estimation block 1018 and confidence level indicator 1020operate as described above with respect to FIG. 10A. During operation,however, filter coefficient selection block 1032 adaptively detects theuse case best represented by radar ADC data 1010. For example, filtercoefficient selection block 1032 may determine whether the user is usinga wrist strap, arm strap, or chest strap, and loads the correspondingcoefficients that were derived during the self-calibration procedureflow 1010 shown in FIG. 10A. In one example, filter coefficientselection block 1032 may include the functionality of blocks 812, 816,818 and 820 shown in FIG. 8.

In various embodiments, filter coefficient selection block determinesthe set of coefficients based on signal path characteristics of themonitoring scenario and the particular portions of the body beingmonitored. An initial set of coefficients are first selected duringself-calibration as described above with respect to FIG. 10A. Thesecoefficients may be adaptively updated as described hereinabove withrespect to FIG. 9. Once the coefficients for different use cases arederived, a particular use case is identified for operation as describedabove with respect to block 816 of FIG. 8, and the coefficientscorresponding to the selected use case are selected as filtercoefficients. For example, if filter coefficient selection block 1032determines that radar ADC data 1010 is obtained in a system in which themillimeter-wave radar sensor is coupled to the user's wrist via a wriststrap or a wrist watch, then the applicable coefficients are loaded intoheartbeat signal filter 1014. On the other hand, if filter coefficientselection block 1032 determines that radar ADC data 1010 is obtained ina system in which the millimeter-wave radar sensor is coupled to theuser's chest via a chest strap, then the coefficients applicable to thechest strap are loaded into heartbeat signal filter 1014.

FIG. 11 illustrates a block diagram of an embodiment artery/veindetection method 1014 situated in the context of other processing stepsthat occur prior to and after the artery/vein detection method 1014. Asshown, range FFT block 1012 performs a range FFT of radar ADC data 1010.A target range detection is performed on the range FFT and the output oftarget range detection block 1102 is monitored by monitor radarslow-time block 1104. In some embodiments, target range selection block1102 extracts the range gates with the highest response, and monitorradar slow-time block 1104 monitors the extracted range gates by storingthe slow-time radar data along the detected range bins.

Artery/vein detection block 1014 determines whether the extracted rangegates represent an artery or a vein by applying heartrate vital-Dopplerfilters 1106 to the values of the extracted range gates. In someembodiments, vital-Doppler filters 1106 include low bandwidth filteringat 0.6 Hz-3 Hz. The output of heartrate micro-Doppler filters 1106 issmoothed using smoothing filters 1108, and vital Doppler detection block1110 filters the output of smoothing filters 1108 in order to detectwhether or not a heartbeat signal is present. In some embodiments, vitalDoppler detection block 1110 is implemented as a threshold detector todiscriminate between valid vital signal and noise.

Vital Doppler detection block 1110 compares the output of smoothingfilters 1108 with a predetermined threshold. In some embodiments, thepredetermined threshold may be about 3 dB above the noise floor.However, in alternative embodiments, other threshold values may be used.If the output of vital Doppler detection block 1110 exceeds thepredetermined threshold, a potential artery/vein is considered to bedetected, and the set of detected range bins are process by heartrateestimation pipeline 1114.

Referring now to FIG. 12, a block diagram of a processing system 1200 isprovided in accordance with an embodiment of the present invention. Theprocessing system 1200 depicts a general-purpose platform and thegeneral components and functionality that may be used to implementportions of the embodiment vital signal sensing system and/or anexternal computer or processing device interfaced to the embodimentvital signal sending system. The processing system 1200 may include, forexample, a central processing unit (CPU) 1202, memory 1204, and a massstorage device 1206 connected to a bus 1208 configured to perform theprocesses discussed above. The processing system 1200 may furtherinclude, if desired or needed, a video adapter 1210 to provideconnectivity to a local display 1212 and an input-output (I/O) Adapter1214 to provide an input/output interface for one or more input/outputdevices 616, such as a mouse, a keyboard, printer, tape drive, CD drive,or the like.

The processing system 1200 also includes a network interface 1218, whichmay be implemented using a network adaptor configured to be coupled to awired link, such as an Ethernet cable, USB interface, or the like,and/or a wireless/cellular link for communications with a network 1220.The network interface 1218 may also comprise a suitable receiver andtransmitter for wireless communications. It should be noted that theprocessing system 1200 may include other components. For example, theprocessing system 1200 may include power supplies, cables, amotherboard, removable storage media, cases, and the like. These othercomponents, although not shown, are considered part of the processingsystem 1200.

Example embodiments of the present invention are summarized here. Otherembodiments can also be understood from the entirety of thespecification and the claims filed herein.

Example 1. A device for measuring vital signals includes a first circuitboard layer comprising a first insulator material; a first integratedcircuit disposed on the first circuit board layer, the first integratedcircuit including a millimeter-wave radar sensor and a digital interfaceconfigured to provide digitized baseband radar signals; a secondintegrated circuit coupled to the first integrated circuit and disposedon the first circuit board layer, the second integrated circuitincluding a digital signal processor (DSP) configured to determine vitalsignal information based on the digitized baseband radar signals; asecond circuit board layer including a second insulator material, thesecond circuit board layer having a first surface disposed over a firstsurface of the first circuit board layer; a transmit antenna disposed onthe second circuit board layer and coupled to the first integratedcircuit; and a receive antenna disposed on the second circuit boardlayer and coupled to the first integrated circuit.

Example 2. The device of example 1, where the first insulator materialis the same as the second insulator material.

Example 3. The device of example 1 or 2, further including a thirdintegrated circuit disposed on the first circuit board layer and coupledto the second integrated circuit, wherein the third integrated circuitincludes a memory.

Example 4. The device of one of examples 1-3, where the first integratedcircuit is disposed on a second surface of the first circuit board layeropposite the first surface.

Example 5. The device of claim 4, where the second integrated circuit isdisposed on the second surface of the first circuit board layer oppositethe first surface of the first circuit board layer.

Example 6. The device of example 4, where the second integrated circuitis disposed within the first surface of the first circuit board layer.

Example 7. The device of one of examples 4-6, where the transmit antennaand the receive antenna include a conductive material disposed on asecond surface of the second circuit board layer opposite the firstsurface of the second circuit board layer; the transmit antenna iscoupled to the first integrated circuit via a first via that extendsthrough the first circuit board layer and the second circuit boardlayer; and the receive antenna is coupled to the first integratedcircuit via a first via that extends through the first circuit boardlayer and the second circuit board layer.

Example 8. The device of one of examples 4-7, further including a groundplane having a conductive layer disposed between the first circuit boardlayer and the second circuit board layer.

Example 9. The device of one of examples 4-7, further including a thirdcircuit board layer disposed between the first circuit board layer andthe second circuit board layer.

Example 10. The device of one of examples 1 or 2, where the firstintegrated circuit is stacked on top of the second integrated circuit;the first integrated circuit is embedded within the first surface of thefirst circuit board layer; and the second integrated circuit is embeddedwithin a second surface of the first circuit board layer opposite thefirst surface of the first circuit board layer.

Example 11. The device of claim 10, further including a third integratedcircuit disposed next to the second integrated circuit, wherein thefirst integrated circuit is further stacked on top of the thirdintegrated circuit, a first portion of a first surface of the firstintegrated circuit is adjacent to a first surface of the secondintegrated circuit, a second portion of the first surface of the firstintegrated circuit is adjacent to a first surface of the thirdintegrated circuit, and the third integrated circuit comprises a memory.

Example 12. The device of one of examples 10 and 11, where the transmitantenna and the receive antenna include a conductive material disposedon a second surface of the second circuit board layer opposite the firstsurface of the second circuit board layer; the transmit antenna iscoupled to the first integrated circuit via a first via that extendsthrough the second circuit board layer; and the receive antenna iscoupled to the first integrated circuit via a second via that extendsthrough the second circuit board layer.

Example 13. A device for measuring vital signals including aredistribution layer comprising an insulating material; a firstintegrated circuit having a first surface disposed on a first side ofthe redistribution layer, the first integrated circuit including amillimeter-wave radar sensor and a digital interface configured toprovide digitized baseband radar signals; a second integrated circuithaving a first surface disposed on the first side of the redistributionlayer and coupled to the first integrated circuit, the second integratedcircuit including a digital signal processor DSP configured to determinevital signal information based on the digitized baseband radar signals;a transmit antenna disposed in the redistribution layer and coupled tothe first integrated circuit via a first conductive layer of theredistribution layer; a receive antenna disposed in the redistributionlayer coupled to the first integrated circuit via a first conductivelayer of the redistribution layer; and a molding material disposed overa second side of the first integrated circuit, a second side of thesecond integrated circuit and the first side of the redistributionlayer.

Example 14. The device of example 13, where the transmit antenna and thereceive antenna are implemented in the first conductive layer; and thefirst conductive layer is disposed at the first surface of theredistribution layer.

Example 15. The device of one of examples 13 or 14, where theredistribution layer, first integrated circuit, second integratedcircuit, transmit antenna, receive antenna and molding material form anembedded wafer level ball grid array (eWLB) package.

Example 16. The device of example 15, where the transmit antenna and thereceive antenna are disposed in a fan out area of the eWLB package.

Example 17. A system including a wearable object configured to be wornby a person; and a millimeter-wave radar system mounted on the wearableobject, the millimeter-wave radar system including a circuit board,millimeter-wave radar sensor disposed on the circuit board, a pluralityof antennas coupled to the millimeter-wave radar sensor and disposed onthe circuit board adjacent to the millimeter-wave radar sensor, and aprocessing circuit coupled to the millimeter-wave radar sensor anddisposed on the circuit board, where the processing circuit isconfigured to determine vital signal information of the person based onoutput from the millimeter-wave radar sensor.

Example 18. The system of example 17, where the wearable object includesa wrist band.

Example 19. The system of example 17, where the wearable object includesa chest strap.

Example 20. The system of one of examples 17-19, where the vital signalinformation includes a heart rate.

Example 21. The system of one of examples 17-20, where the processingcircuit is further configured to instruct the millimeter-wave radarsensor to perform a first set of radar measurements to produce a firstset of radar data; determine a first set of range gate measurements fromthe first set of radar data; determine high response range gates fromthe first set of range gate measurements; apply a correction filter tothe determined high response range gates in slow-time to producecorrected range gate data, the correction filter configured to correctfor a manner in which the millimeter-wave radar sensor is coupled to theperson via the wearable object; and apply a vital signal filter to thecorrected range gate data to determine the vital signal information ofthe person.

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

What is claimed is:
 1. A device for measuring vital signals, the devicecomprising: a first circuit board layer comprising a first insulatormaterial; a first integrated circuit disposed on the first circuit boardlayer, the first integrated circuit comprising a millimeter-wave radarsensor and a digital interface configured to provide digitized basebandradar signals; a second integrated circuit coupled to the firstintegrated circuit and disposed on the first circuit board layer, thesecond integrated circuit comprising a digital signal processor (DSP)configured to determine vital signal information based on the digitizedbaseband radar signals; a second circuit board layer comprising a secondinsulator material, the second circuit board layer having a firstsurface disposed over a first surface of the first circuit board layer;a transmit antenna disposed on the second circuit board layer andcoupled to the first integrated circuit; and a receive antenna disposedon the second circuit board layer and coupled to the first integratedcircuit.
 2. The device of claim 1, wherein the first insulator materialis the same as the second insulator material.
 3. The device of claim 1,further comprising a third integrated circuit disposed on the firstcircuit board layer and coupled to the second integrated circuit,wherein the third integrated circuit comprises a memory.
 4. The deviceof claim 1, wherein the first integrated circuit is disposed on a secondsurface of the first circuit board layer opposite the first surface. 5.The device of claim 4, wherein the second integrated circuit is disposedon the second surface of the first circuit board layer opposite thefirst surface of the first circuit board layer.
 6. The device of claim4, wherein the second integrated circuit is disposed within the firstsurface of the first circuit board layer.
 7. The device of claim 4,wherein: the transmit antenna and the receive antenna comprise aconductive material disposed on a second surface of the second circuitboard layer opposite the first surface of the second circuit boardlayer; the transmit antenna is coupled to the first integrated circuitvia a first via that extends through the first circuit board layer andthe second circuit board layer; and the receive antenna is coupled tothe first integrated circuit via a first via that extends through thefirst circuit board layer and the second circuit board layer.
 8. Thedevice of claim 4, further comprising a ground plane, the ground planecomprising a conductive layer disposed between the first circuit boardlayer and the second circuit board layer.
 9. The device of claim 4,further comprising a third circuit board layer disposed between thefirst circuit board layer and the second circuit board layer.
 10. Thedevice of claim 1, wherein: the first integrated circuit is stacked ontop of the second integrated circuit; the first integrated circuit isembedded within the first surface of the first circuit board layer; andthe second integrated circuit is embedded within a second surface of thefirst circuit board layer opposite the first surface of the firstcircuit board layer.
 11. The device of claim 10, further comprising athird integrated circuit disposed next to the second integrated circuit,wherein the first integrated circuit is further stacked on top of thethird integrated circuit, a first portion of a first surface of thefirst integrated circuit is adjacent to a first surface of the secondintegrated circuit, a second portion of the first surface of the firstintegrated circuit is adjacent to a first surface of the thirdintegrated circuit, and the third integrated circuit comprises a memory.12. The device of claim 10, wherein: the transmit antenna and thereceive antenna comprise a conductive material disposed on a secondsurface of the second circuit board layer opposite the first surface ofthe second circuit board layer; the transmit antenna is coupled to thefirst integrated circuit via a first via that extends through the secondcircuit board layer; and the receive antenna is coupled to the firstintegrated circuit via a second via that extends through the secondcircuit board layer.
 13. A device for measuring vital signals, thedevice comprising: a redistribution layer comprising an insulatingmaterial; a first integrated circuit having a first surface disposed ona first side of the redistribution layer, the first integrated circuitcomprising a millimeter-wave radar sensor and a digital interfaceconfigured to provide digitized baseband radar signals; a secondintegrated circuit having a first surface disposed on the first side ofthe redistribution layer and coupled to the first integrated circuit,the second integrated circuit comprising a digital signal processor DSPconfigured to determine vital signal information based on the digitizedbaseband radar signals; a transmit antenna disposed in theredistribution layer and coupled to the first integrated circuit via afirst conductive layer of the redistribution layer; a receive antennadisposed in the redistribution layer coupled to the first integratedcircuit via a first conductive layer of the redistribution layer; and amolding material disposed over a second side of the first integratedcircuit, a second side of the second integrated circuit and the firstside of the redistribution layer.
 14. The device of claim 13, wherein:the transmit antenna and the receive antenna are implemented in thefirst conductive layer; and the first conductive layer is disposed atthe first surface of the redistribution layer.
 15. The device of claim13, wherein the redistribution layer, first integrated circuit, secondintegrated circuit, transmit antenna, receive antenna and moldingmaterial form an embedded wafer level ball grid array (eWLB) package.16. The device of claim 15, wherein the transmit antenna and the receiveantenna are disposed in a fan out area of the eWLB package.
 17. A systemcomprising: a wearable object configured to be worn by a person; and amillimeter-wave radar system mounted on the wearable object, themillimeter-wave radar system comprising a circuit board, millimeter-waveradar sensor disposed on the circuit board, a plurality of antennascoupled to the millimeter-wave radar sensor and disposed on the circuitboard adjacent to the millimeter-wave radar sensor, and a processingcircuit coupled to the millimeter-wave radar sensor and disposed on thecircuit board, the processing circuit is configured to determine vitalsignal information of the person based on output from themillimeter-wave radar sensor.
 18. The system of claim 17, wherein thewearable object comprises a wrist band.
 19. The system of claim 17,wherein the wearable object comprises a chest strap.
 20. The system ofclaim 17, wherein the vital signal information comprises a heart rate.21. The system of claim 17, wherein the processing circuit is furtherconfigured to: instruct the millimeter-wave radar sensor to perform afirst set of radar measurements to produce a first set of radar data;determine a first set of range gate measurements from the first set ofradar data; determine high response range gates from the first set ofrange gate measurements; apply a correction filter to the determinedhigh response range gates in slow-time to produce corrected range gatedata, the correction filter configured to correct for a manner in whichthe millimeter-wave radar sensor is coupled to the person via thewearable object; and apply a vital signal filter to the corrected rangegate data to determine the vital signal information of the person.